Various services are available for users connected to a communication network. These services include, without limiting to these, services available over the Internet or various intranet applications or services available over telephone networks. In the following services available via a network will be referenced to as network services. The network services are available from sources connected to the communication networks. A source may be an entity such as a server or other data storage and processing device. The term service provider will be used to refer to any source where a network service is available.
The number of network services, which are provided over communication networks, increases constantly, and the variety of network services increases as well. Network services may be implemented using proprietary techniques, as long as a common interface for accessing the network services is provided. Currently Uniform Resource Identifiers (URIs), HyperText Markup Language (HTML) and HyperText Transfer Protocol (HTTP) are examples of basic protocols for accessing network services. These techniques are well known by the skilled person, and are therefore not described in any greater detail here.
The World Wide Web Consortium (W3C) has been developing Semantic Web services in a bottom-up fashion, where the basic building block is Recourse Description Framework (RDF) technology. This technology provides a data model for expressing machine-understandable semantics.
Web Services technologies, on the other hand, have been developed and introduced by software vendors. Web Services is a set of technologies that address the communication between different information processing architectures over a network element. W3C is standardising technologies relating to Web Services, and generally Web Services are currently understood as Simple Object Access Protocol (SOAP) layered services on the Internet. SOAP enables the invocation of services using a protocol payload encoded in Extensible Markup Language (XML) and carried over various protocols such as HyperText Transfer Protocol or Simple Mail Transfer Protocol (SMTP).
Network services can be described in a declarative fashion using Web Services Description Language (WSDL); the current versions of WSDL are version 1.1 and version 1.2. WSDL embeds information about data types, message structures, interaction models (port types), protocol bindings and service points.
Currently Web Services is understood as software components that expose their functionality using simple object Access Protocol (SOAP) and are able to describe this functionality using Web Services Description Language (WSDL) technology. One problem with Web Services is the lack of automating composite services where multiple services are automatically invoked in order to have a set of input data mapped to a set of output data. In addition, the current technologies do not address automated reachability analysis over the service descriptions.
It shall be appreciated that although the above discussed problems relate to Web services, similar disadvantages may be associated with network services pursuant to other frameworks or with services within an information technology system as well. Thus the description is not limited to Web Services, but discusses them as examples.